If Type Ia supernovae (SNe Ia) result from a white dwarf being ignited by Roche lobe overflow from a nondegenerate companion, then as the supernova explosion runs into the companion star its ejecta will be shocked, causing an early blue excess in the lightcurve. A handful of these excesses have been found in single-object studies, but inferences about the population of SNe Ia as a whole have been limited because of the rarity of multiwavelength followup within days of explosion. Here we present a threeyear investigation yielding an unbiased sample of nine nearby (z < 0.01) SNe Ia with exemplary early data. The data are truly multiwavelength, covering U BV gri and Swift bandpasses, and also early, with an average first epoch 16.0 days before maximum light. Of the nine objects, three show early blue excesses. We do not find enough statistical evidence to reject the null hypothesis that SNe Ia predominantly arise from Rochelobe-overflowing single-degenerate systems (p = 0.94). When looking at the objects'

We present photometric and spectroscopic observations of SN 2020bio, a double-peaked Type IIb supernova (SN) discovered within a day of explosion, primarily obtained by Las Cumbres Observatory and Swift. SN 2020bio displays a rapid and long-lasting initial decline throughout the first week of its light curve, similar to other well-studied Type IIb SNe. This early-time emission is thought to originate from the cooling of the extended outer envelope of the progenitor star that is shock-heated by the SN explosion. We compare SN 2020bio to a sample of other double-peaked Type IIb SNe to investigate its progenitor properties. Analytical model fits to the early-time emission give progenitor radius (≈ 100-1500 R ) and H-rich envelope mass (≈ 0.01-0.5 M ) estimates that are consistent with other Type IIb SNe. However, SN 2020bio displays several peculiarities, including: 1) weak H spectral features and narrow emission lines indicative of pre-existing circumstellar material; 2) an underluminous secondary light curve peak which implies a small amount of synthesized 56 Ni (M Ni ≈ 0.02 M ); and 3) lowluminosity nebular [O I] features. These observations are more consistent with a lower-mass progenitor (M ZAMS ≈ 12 M ) that was stripped of most of its H envelope before exploding. This study adds to the growing diversity in the observed properties of Type IIb SNe and their progenitors.